The invention relates to apparatus and techniques for enabling computers, especially personal computers, to economically and flexibly perform various instrumention functions.
With the recent widespread use of personal computers for home use and business uses as well as engineering and scientific uses, efforts have been made and products have been developed to expand the possible uses of personal computers into various other control and instrumentation functions that typically have been performed by specialized machines. For example, one manufacturer makes a printed circuit board that can be plugged into an Apple computer to make it function as an oscilloscope. There are a variety of other such applications in which printed circuit boards are being manufactured to be plugged directly into vacant board slots that are provided in most personal computers.
Although this approach to expanding use of personal computers appears promising, there are a number of problems that up to now have prevented such "plug-in" printed circuit boards from being more widely used than they are. For example, one fairly large market for plug-in computer cards would be in the area of enabling small manufacturing concerns to accomplish automated process control and/or automatic testing by means of printed circuit board systems that could be plugged into inexpensive personal computers. The types of functions that need to be accomplished by means of such printed circuit boards include receiving (usually by means of cables) both digital signals and analog signals produced by equipment that controls and/or monitors manufacturing or testing functions. Another function that frequently needs to be performed by instrumentation includes transmitting of both digital signals and analog signals to equipment involved in the control of and monitoring of manufacturing or testing operations.
Due to the fact that there are a very large number of different manufacturers of personal computers presently on the market, there is no "standard" bus, into which all "instrumentation boards" for a particular function can be plugged. Therefore, instrumentation boards that are capable of performing a particular instrumentation function need to be specially designed for each different brand or type of personal computer. This adds substantially to the product development costs, manufacturing costs, and the servicing costs of a particular type of instrumentation board, if it is to be made available to users of many different makes of personal computers. Such increased costs, of course, limit the market. Another problem with this approach is that in order to use an instrumentation plug-in card to enable a personal computer to perform a particular instrumentation function, especially a complex instrumentation function, specialized software also needs to be provided. At the present state of the art, in order to accomplish the objective of providing instrumentation functions by "expanding" personal computers by plugging in specialized instrumentation boards, every different kind of instrumentation function must be implemented on a different printed circuit board, and this must be done for each different make of personal computer, and different corresponding software must be provided for each different type of instrumentation board and personal computer used.
Although a fairly high degree of "modularity" has been achieved for various digital functions and components (due to the widespread use of "bus-oriented" digital equipment structures), the entirely different nature of analog signals, up to now, has not been commonly thought to be susceptible to or suitable for "bus-oriented" structures for processing analog signals in electronic instrumentation systems.
In view of the foregoing circumstances, it is clear that there remains an unmet need for providing plug-in instrumentation modules for connection to a wide variety of computer bus structures while minimizing the complexity of, and the portion of the cost, that are attributable to differences between the bus structures and internal operations of various popular personal computer, so that economies of scale can be achieved, both in hardware and software.